The present invention relates to a starter, particularly to a starter for starting the engine of a vehicle.
FIG. 1 shows a conventional starter 1 for starting the engine of a vehicle. The DC motor 5 of the starter 1 has a yoke 2 constituting the magnetic circuit of the motor and the outside portion of the starter, a bowl-shaped rear cover 4 secured to the rear open end (which is the left-hand end as to FIG. 1) of the yoke by longitudinal bolts 3, an armature core 6, an armature shaft 7 fitted with the core, a commutator 8 mounted on the shaft at the rear end thereof, and brush holders 9b supporting brushes 9a and disposed at equal circumferential intervals around the commutator. The bowl-shaped rear cover 4 is made of a synthetic resin and fitted to the rear open end of the yoke 2 so that the rear cover and the brushes 9a surround the commutator 8. The armature shaft 7 is supported at the rear end thereof by a bearing 10 provided in the recess of the central portion of the end wall 4a of the rear cover 4. A mounting plate 11, to which the brush holders 9b are attached, is secured to the inside surface of the end wall 4a of the rear cover 4 by screws 12. The plus brush 9a is connected to a lead wire 13 connected to one contact of an electromagnetic switch not shown in FIG. 1. The minus brush 9a is connected to a lead wire 14 connected to a ground terminal.
Since the tensile forces of the longitudinal bolts 3 for securing the rear cover 4 to the yoke 2 act on the end wall 4a of the rear cover made of the synthetic resin, the end wall undergoes bending and compression so that the absolute strength, creep strength and vibration resistance of the end wall are adversely affected. Particularly, the notched portions of the rear cover 4, which are provided so that the lead wires 13 and 14 are laid through the notched portions, undergo stress concentration so that the portions are likely to be damaged. This is a problem. Besides, since the lead wire 14 and the ground terminal need to be provided to ground the minus brush 9a, the constitution of the starter is more complicated. This is another problem.